import {
        AnimationClip,
        Bone,
        Box3,
        BufferAttribute,
        BufferGeometry,
        CanvasTexture,
        ClampToEdgeWrapping,
        Color,
        DirectionalLight,
        DoubleSide,
        FileLoader,
        FrontSide,
        Group,
        ImageBitmapLoader,
        InterleavedBuffer,
        InterleavedBufferAttribute,
        Interpolant,
        InterpolateDiscrete,
        InterpolateLinear,
        Line,
        LineBasicMaterial,
        LineLoop,
        LineSegments,
        LinearFilter,
        LinearMipmapLinearFilter,
        LinearMipmapNearestFilter,
        Loader,
        LoaderUtils,
        Material,
        MathUtils,
        Matrix4,
        Mesh,
        MeshBasicMaterial,
        MeshPhysicalMaterial,
        MeshStandardMaterial,
        MirroredRepeatWrapping,
        NearestFilter,
        NearestMipmapLinearFilter,
        NearestMipmapNearestFilter,
        NumberKeyframeTrack,
        Object3D,
        OrthographicCamera,
        PerspectiveCamera,
        PointLight,
        Points,
        PointsMaterial,
        PropertyBinding,
        QuaternionKeyframeTrack,
        RGBFormat,
        RepeatWrapping,
        Skeleton,
        SkinnedMesh,
        Sphere,
        SpotLight,
        TangentSpaceNormalMap,
        TextureLoader,
        TriangleFanDrawMode,
        TriangleStripDrawMode,
        Vector2,
        Vector3,
        VectorKeyframeTrack,
        sRGBEncoding
} from "./three.module.js";

var GLTFLoader = ( function () {

        function GLTFLoader( manager ) {

                Loader.call( this, manager );

                this.dracoLoader = null;
                this.ddsLoader = null;
                this.ktx2Loader = null;
                this.meshoptDecoder = null;

                this.pluginCallbacks = [];

                this.register( function ( parser ) {

                        return new GLTFMaterialsClearcoatExtension( parser );

                } );

                this.register( function ( parser ) {

                        return new GLTFTextureBasisUExtension( parser );

                } );

                this.register( function ( parser ) {

                        return new GLTFTextureWebPExtension( parser );

                } );

                this.register( function ( parser ) {

                        return new GLTFMaterialsTransmissionExtension( parser );

                } );

                this.register( function ( parser ) {

                        return new GLTFLightsExtension( parser );

                } );

                this.register( function ( parser ) {

                        return new GLTFMeshoptCompression( parser );

                } );

        }

        GLTFLoader.prototype = Object.assign( Object.create( Loader.prototype ), {

                constructor: GLTFLoader,

                load: function ( url, onLoad, onProgress, onError ) {

                        var scope = this;

                        var resourcePath;

                        if ( this.resourcePath !== '' ) {

                                resourcePath = this.resourcePath;

                        } else if ( this.path !== '' ) {

                                resourcePath = this.path;

                        } else {

                                resourcePath = LoaderUtils.extractUrlBase( url );

                        }

                        // Tells the LoadingManager to track an extra item, which resolves after
                        // the model is fully loaded. This means the count of items loaded will
                        // be incorrect, but ensures manager.onLoad() does not fire early.
                        this.manager.itemStart( url );

                        var _onError = function ( e ) {

                                if ( onError ) {

                                        onError( e );

                                } else {

                                        console.error( e );

                                }

                                scope.manager.itemError( url );
                                scope.manager.itemEnd( url );

                        };

                        var loader = new FileLoader( this.manager );

                        loader.setPath( this.path );
                        loader.setResponseType( 'arraybuffer' );
                        loader.setRequestHeader( this.requestHeader );
                        loader.setWithCredentials( this.withCredentials );

                        loader.load( url, function ( data ) {

                                try {

                                        scope.parse( data, resourcePath, function ( gltf ) {

                                                onLoad( gltf );

                                                scope.manager.itemEnd( url );

                                        }, _onError );

                                } catch ( e ) {

                                        _onError( e );

                                }

                        }, onProgress, _onError );

                },

                setDRACOLoader: function ( dracoLoader ) {

                        this.dracoLoader = dracoLoader;
                        return this;

                },

                setDDSLoader: function ( ddsLoader ) {

                        this.ddsLoader = ddsLoader;
                        return this;

                },

                setKTX2Loader: function ( ktx2Loader ) {

                        this.ktx2Loader = ktx2Loader;
                        return this;

                },

                setMeshoptDecoder: function ( meshoptDecoder ) {

                        this.meshoptDecoder = meshoptDecoder;
                        return this;

                },

                register: function ( callback ) {

                        if ( this.pluginCallbacks.indexOf( callback ) === - 1 ) {

                                this.pluginCallbacks.push( callback );

                        }

                        return this;

                },

                unregister: function ( callback ) {

                        if ( this.pluginCallbacks.indexOf( callback ) !== - 1 ) {

                                this.pluginCallbacks.splice( this.pluginCallbacks.indexOf( callback ), 1 );

                        }

                        return this;

                },

                parse: function ( data, path, onLoad, onError ) {

                        var content;
                        var extensions = {};
                        var plugins = {};

                        if ( typeof data === 'string' ) {

                                content = data;

                        } else {

                                var magic = LoaderUtils.decodeText( new Uint8Array( data, 0, 4 ) );

                                if ( magic === BINARY_EXTENSION_HEADER_MAGIC ) {

                                        try {

                                                extensions[ EXTENSIONS.KHR_BINARY_GLTF ] = new GLTFBinaryExtension( data );

                                        } catch ( error ) {

                                                if ( onError ) onError( error );
                                                return;

                                        }

                                        content = extensions[ EXTENSIONS.KHR_BINARY_GLTF ].content;

                                } else {

                                        content = LoaderUtils.decodeText( new Uint8Array( data ) );

                                }

                        }

                        var json = JSON.parse( content );

                        if ( json.asset === undefined || json.asset.version[ 0 ] < 2 ) {

                                if ( onError ) onError( new Error( 'THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported.' ) );
                                return;

                        }

                        var parser = new GLTFParser( json, {

                                path: path || this.resourcePath || '',
                                crossOrigin: this.crossOrigin,
                                manager: this.manager,
                                ktx2Loader: this.ktx2Loader,
                                meshoptDecoder: this.meshoptDecoder

                        } );

                        parser.fileLoader.setRequestHeader( this.requestHeader );

                        for ( var i = 0; i < this.pluginCallbacks.length; i ++ ) {

                                var plugin = this.pluginCallbacks[ i ]( parser );
                                plugins[ plugin.name ] = plugin;

                                // Workaround to avoid determining as unknown extension
                                // in addUnknownExtensionsToUserData().
                                // Remove this workaround if we move all the existing
                                // extension handlers to plugin system
                                extensions[ plugin.name ] = true;

                        }

                        if ( json.extensionsUsed ) {

                                for ( var i = 0; i < json.extensionsUsed.length; ++ i ) {

                                        var extensionName = json.extensionsUsed[ i ];
                                        var extensionsRequired = json.extensionsRequired || [];

                                        switch ( extensionName ) {

                                                case EXTENSIONS.KHR_MATERIALS_UNLIT:
                                                        extensions[ extensionName ] = new GLTFMaterialsUnlitExtension();
                                                        break;

                                                case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
                                                        extensions[ extensionName ] = new GLTFMaterialsPbrSpecularGlossinessExtension();
                                                        break;

                                                case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
                                                        extensions[ extensionName ] = new GLTFDracoMeshCompressionExtension( json, this.dracoLoader );
                                                        break;

                                                case EXTENSIONS.MSFT_TEXTURE_DDS:
                                                        extensions[ extensionName ] = new GLTFTextureDDSExtension( this.ddsLoader );
                                                        break;

                                                case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
                                                        extensions[ extensionName ] = new GLTFTextureTransformExtension();
                                                        break;

                                                case EXTENSIONS.KHR_MESH_QUANTIZATION:
                                                        extensions[ extensionName ] = new GLTFMeshQuantizationExtension();
                                                        break;

                                                default:

                                                        if ( extensionsRequired.indexOf( extensionName ) >= 0 && plugins[ extensionName ] === undefined ) {

                                                                console.warn( 'THREE.GLTFLoader: Unknown extension "' + extensionName + '".' );

                                                        }

                                        }

                                }

                        }

                        parser.setExtensions( extensions );
                        parser.setPlugins( plugins );
                        parser.parse( onLoad, onError );

                }

        } );

        /* GLTFREGISTRY */

        function GLTFRegistry() {

                var objects = {};

                return  {

                        get: function ( key ) {

                                return objects[ key ];

                        },

                        add: function ( key, object ) {

                                objects[ key ] = object;

                        },

                        remove: function ( key ) {

                                delete objects[ key ];

                        },

                        removeAll: function () {

                                objects = {};

                        }

                };

        }

        /*********************************/
        /********** EXTENSIONS ***********/
        /*********************************/

        var EXTENSIONS = {
                KHR_BINARY_GLTF: 'KHR_binary_glTF',
                KHR_DRACO_MESH_COMPRESSION: 'KHR_draco_mesh_compression',
                KHR_LIGHTS_PUNCTUAL: 'KHR_lights_punctual',
                KHR_MATERIALS_CLEARCOAT: 'KHR_materials_clearcoat',
                KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS: 'KHR_materials_pbrSpecularGlossiness',
                KHR_MATERIALS_TRANSMISSION: 'KHR_materials_transmission',
                KHR_MATERIALS_UNLIT: 'KHR_materials_unlit',
                KHR_TEXTURE_BASISU: 'KHR_texture_basisu',
                KHR_TEXTURE_TRANSFORM: 'KHR_texture_transform',
                KHR_MESH_QUANTIZATION: 'KHR_mesh_quantization',
                EXT_TEXTURE_WEBP: 'EXT_texture_webp',
                EXT_MESHOPT_COMPRESSION: 'EXT_meshopt_compression',
                MSFT_TEXTURE_DDS: 'MSFT_texture_dds'
        };

        /**
         * DDS Texture Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_texture_dds
         *
         */
        function GLTFTextureDDSExtension( ddsLoader ) {

                if ( ! ddsLoader ) {

                        throw new Error( 'THREE.GLTFLoader: Attempting to load .dds texture without importing DDSLoader' );

                }

                this.name = EXTENSIONS.MSFT_TEXTURE_DDS;
                this.ddsLoader = ddsLoader;

        }

        /**
         * Punctual Lights Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
         */
        function GLTFLightsExtension( parser ) {

                this.parser = parser;
                this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;

                // Object3D instance caches
                this.cache = { refs: {}, uses: {} };

        }

        GLTFLightsExtension.prototype._markDefs = function () {

                var parser = this.parser;
                var nodeDefs = this.parser.json.nodes || [];

                for ( var nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex ++ ) {

                        var nodeDef = nodeDefs[ nodeIndex ];

                        if ( nodeDef.extensions
                                && nodeDef.extensions[ this.name ]
                                && nodeDef.extensions[ this.name ].light !== undefined ) {

                                parser._addNodeRef( this.cache, nodeDef.extensions[ this.name ].light );

                        }

                }

        };

        GLTFLightsExtension.prototype._loadLight = function ( lightIndex ) {

                var parser = this.parser;
                var cacheKey = 'light:' + lightIndex;
                var dependency = parser.cache.get( cacheKey );

                if ( dependency ) return dependency;

                var json = parser.json;
                var extensions = ( json.extensions && json.extensions[ this.name ] ) || {};
                var lightDefs = extensions.lights || [];
                var lightDef = lightDefs[ lightIndex ];
                var lightNode;

                var color = new Color( 0xffffff );

                if ( lightDef.color !== undefined ) color.fromArray( lightDef.color );

                var range = lightDef.range !== undefined ? lightDef.range : 0;

                switch ( lightDef.type ) {

                        case 'directional':
                                lightNode = new DirectionalLight( color );
                                lightNode.target.position.set( 0, 0, - 1 );
                                lightNode.add( lightNode.target );
                                break;

                        case 'point':
                                lightNode = new PointLight( color );
                                lightNode.distance = range;
                                break;

                        case 'spot':
                                lightNode = new SpotLight( color );
                                lightNode.distance = range;
                                // Handle spotlight properties.
                                lightDef.spot = lightDef.spot || {};
                                lightDef.spot.innerConeAngle = lightDef.spot.innerConeAngle !== undefined ? lightDef.spot.innerConeAngle : 0;
                                lightDef.spot.outerConeAngle = lightDef.spot.outerConeAngle !== undefined ? lightDef.spot.outerConeAngle : Math.PI / 4.0;
                                lightNode.angle = lightDef.spot.outerConeAngle;
                                lightNode.penumbra = 1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
                                lightNode.target.position.set( 0, 0, - 1 );
                                lightNode.add( lightNode.target );
                                break;

                        default:
                                throw new Error( 'THREE.GLTFLoader: Unexpected light type, "' + lightDef.type + '".' );

                }

                // Some lights (e.g. spot) default to a position other than the origin. Reset the position
                // here, because node-level parsing will only override position if explicitly specified.
                lightNode.position.set( 0, 0, 0 );

                lightNode.decay = 2;

                if ( lightDef.intensity !== undefined ) lightNode.intensity = lightDef.intensity;

                lightNode.name = parser.createUniqueName( lightDef.name || ( 'light_' + lightIndex ) );

                dependency = Promise.resolve( lightNode );

                parser.cache.add( cacheKey, dependency );

                return dependency;

        };

        GLTFLightsExtension.prototype.createNodeAttachment = function ( nodeIndex ) {

                var self = this;
                var parser = this.parser;
                var json = parser.json;
                var nodeDef = json.nodes[ nodeIndex ];
                var lightDef = ( nodeDef.extensions && nodeDef.extensions[ this.name ] ) || {};
                var lightIndex = lightDef.light;

                if ( lightIndex === undefined ) return null;

                return this._loadLight( lightIndex ).then( function ( light ) {

                        return parser._getNodeRef( self.cache, lightIndex, light );

                } );

        };

        /**
         * Unlit Materials Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
         */
        function GLTFMaterialsUnlitExtension() {

                this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;

        }

        GLTFMaterialsUnlitExtension.prototype.getMaterialType = function () {

                return MeshBasicMaterial;

        };

        GLTFMaterialsUnlitExtension.prototype.extendParams = function ( materialParams, materialDef, parser ) {

                var pending = [];

                materialParams.color = new Color( 1.0, 1.0, 1.0 );
                materialParams.opacity = 1.0;

                var metallicRoughness = materialDef.pbrMetallicRoughness;

                if ( metallicRoughness ) {

                        if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {

                                var array = metallicRoughness.baseColorFactor;

                                materialParams.color.fromArray( array );
                                materialParams.opacity = array[ 3 ];

                        }

                        if ( metallicRoughness.baseColorTexture !== undefined ) {

                                pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture ) );

                        }

                }

                return Promise.all( pending );

        };

        /**
         * Clearcoat Materials Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_clearcoat
         */
        function GLTFMaterialsClearcoatExtension( parser ) {

                this.parser = parser;
                this.name = EXTENSIONS.KHR_MATERIALS_CLEARCOAT;

        }

        GLTFMaterialsClearcoatExtension.prototype.getMaterialType = function ( materialIndex ) {

                var parser = this.parser;
                var materialDef = parser.json.materials[ materialIndex ];

                if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;

                return MeshPhysicalMaterial;

        };

        GLTFMaterialsClearcoatExtension.prototype.extendMaterialParams = function ( materialIndex, materialParams ) {

                var parser = this.parser;
                var materialDef = parser.json.materials[ materialIndex ];

                if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {

                        return Promise.resolve();

                }

                var pending = [];

                var extension = materialDef.extensions[ this.name ];

                if ( extension.clearcoatFactor !== undefined ) {

                        materialParams.clearcoat = extension.clearcoatFactor;

                }

                if ( extension.clearcoatTexture !== undefined ) {

                        pending.push( parser.assignTexture( materialParams, 'clearcoatMap', extension.clearcoatTexture ) );

                }

                if ( extension.clearcoatRoughnessFactor !== undefined ) {

                        materialParams.clearcoatRoughness = extension.clearcoatRoughnessFactor;

                }

                if ( extension.clearcoatRoughnessTexture !== undefined ) {

                        pending.push( parser.assignTexture( materialParams, 'clearcoatRoughnessMap', extension.clearcoatRoughnessTexture ) );

                }

                if ( extension.clearcoatNormalTexture !== undefined ) {

                        pending.push( parser.assignTexture( materialParams, 'clearcoatNormalMap', extension.clearcoatNormalTexture ) );

                        if ( extension.clearcoatNormalTexture.scale !== undefined ) {

                                var scale = extension.clearcoatNormalTexture.scale;

                                materialParams.clearcoatNormalScale = new Vector2( scale, scale );

                        }

                }

                return Promise.all( pending );

        };

        /**
         * Transmission Materials Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_transmission
         * Draft: https://github.com/KhronosGroup/glTF/pull/1698
         */
        function GLTFMaterialsTransmissionExtension( parser ) {

                this.parser = parser;
                this.name = EXTENSIONS.KHR_MATERIALS_TRANSMISSION;

        }

        GLTFMaterialsTransmissionExtension.prototype.getMaterialType = function ( materialIndex ) {

                var parser = this.parser;
                var materialDef = parser.json.materials[ materialIndex ];

                if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) return null;

                return MeshPhysicalMaterial;

        };

        GLTFMaterialsTransmissionExtension.prototype.extendMaterialParams = function ( materialIndex, materialParams ) {

                var parser = this.parser;
                var materialDef = parser.json.materials[ materialIndex ];

                if ( ! materialDef.extensions || ! materialDef.extensions[ this.name ] ) {

                        return Promise.resolve();

                }

                var pending = [];

                var extension = materialDef.extensions[ this.name ];

                if ( extension.transmissionFactor !== undefined ) {

                        materialParams.transmission = extension.transmissionFactor;

                }

                if ( extension.transmissionTexture !== undefined ) {

                        pending.push( parser.assignTexture( materialParams, 'transmissionMap', extension.transmissionTexture ) );

                }

                return Promise.all( pending );

        };

        /**
         * BasisU Texture Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_basisu
         */
        function GLTFTextureBasisUExtension( parser ) {

                this.parser = parser;
                this.name = EXTENSIONS.KHR_TEXTURE_BASISU;

        }

        GLTFTextureBasisUExtension.prototype.loadTexture = function ( textureIndex ) {

                var parser = this.parser;
                var json = parser.json;

                var textureDef = json.textures[ textureIndex ];

                if ( ! textureDef.extensions || ! textureDef.extensions[ this.name ] ) {

                        return null;

                }

                var extension = textureDef.extensions[ this.name ];
                var source = json.images[ extension.source ];
                var loader = parser.options.ktx2Loader;

                if ( ! loader ) {

                        if ( json.extensionsRequired && json.extensionsRequired.indexOf( this.name ) >= 0 ) {

                                throw new Error( 'THREE.GLTFLoader: setKTX2Loader must be called before loading KTX2 textures' );

                        } else {

                                // Assumes that the extension is optional and that a fallback texture is present
                                return null;

                        }

                }

                return parser.loadTextureImage( textureIndex, source, loader );

        };

        /**
         * WebP Texture Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_webp
         */
        function GLTFTextureWebPExtension( parser ) {

                this.parser = parser;
                this.name = EXTENSIONS.EXT_TEXTURE_WEBP;
                this.isSupported = null;

        }

        GLTFTextureWebPExtension.prototype.loadTexture = function ( textureIndex ) {

                var name = this.name;
                var parser = this.parser;
                var json = parser.json;

                var textureDef = json.textures[ textureIndex ];

                if ( ! textureDef.extensions || ! textureDef.extensions[ name ] ) {

                        return null;

                }

                var extension = textureDef.extensions[ name ];
                var source = json.images[ extension.source ];
                var loader = source.uri ? parser.options.manager.getHandler( source.uri ) : parser.textureLoader;

                return this.detectSupport().then( function ( isSupported ) {

                        if ( isSupported ) return parser.loadTextureImage( textureIndex, source, loader );

                        if ( json.extensionsRequired && json.extensionsRequired.indexOf( name ) >= 0 ) {

                                throw new Error( 'THREE.GLTFLoader: WebP required by asset but unsupported.' );

                        }

                        // Fall back to PNG or JPEG.
                        return parser.loadTexture( textureIndex );

                } );

        };

        GLTFTextureWebPExtension.prototype.detectSupport = function () {

                if ( ! this.isSupported ) {

                        this.isSupported = new Promise( function ( resolve ) {

                                var image = new Image();

                                // Lossy test image. Support for lossy images doesn't guarantee support for all
                                // WebP images, unfortunately.
                                image.src = '';

                                image.onload = image.onerror = function () {

                                        resolve( image.height === 1 );

                                };

                        } );

                }

                return this.isSupported;

        };

        /**
        * meshopt BufferView Compression Extension
        *
        * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_meshopt_compression
        */
        function GLTFMeshoptCompression( parser ) {

                this.name = EXTENSIONS.EXT_MESHOPT_COMPRESSION;
                this.parser = parser;

        }

        GLTFMeshoptCompression.prototype.loadBufferView = function ( index ) {

                var json = this.parser.json;
                var bufferView = json.bufferViews[ index ];

                if ( bufferView.extensions && bufferView.extensions[ this.name ] ) {

                        var extensionDef = bufferView.extensions[ this.name ];

                        var buffer = this.parser.getDependency( 'buffer', extensionDef.buffer );
                        var decoder = this.parser.options.meshoptDecoder;

                        if ( ! decoder || ! decoder.supported ) {

                                if ( json.extensionsRequired && json.extensionsRequired.indexOf( this.name ) >= 0 ) {

                                        throw new Error( 'THREE.GLTFLoader: setMeshoptDecoder must be called before loading compressed files' );

                                } else {

                                        // Assumes that the extension is optional and that fallback buffer data is present
                                        return null;

                                }

                        }

                        return Promise.all( [ buffer, decoder.ready ] ).then( function ( res ) {

                                var byteOffset = extensionDef.byteOffset || 0;
                                var byteLength = extensionDef.byteLength || 0;

                                var count = extensionDef.count;
                                var stride = extensionDef.byteStride;

                                var result = new ArrayBuffer( count * stride );
                                var source = new Uint8Array( res[ 0 ], byteOffset, byteLength );

                                decoder.decodeGltfBuffer( new Uint8Array( result ), count, stride, source, extensionDef.mode, extensionDef.filter );
                                return result;

                        } );

                } else {

                        return null;

                }

        };

        /* BINARY EXTENSION */
        var BINARY_EXTENSION_HEADER_MAGIC = 'glTF';
        var BINARY_EXTENSION_HEADER_LENGTH = 12;
        var BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4E4F534A, BIN: 0x004E4942 };

        function GLTFBinaryExtension( data ) {

                this.name = EXTENSIONS.KHR_BINARY_GLTF;
                this.content = null;
                this.body = null;

                var headerView = new DataView( data, 0, BINARY_EXTENSION_HEADER_LENGTH );

                this.header = {
                        magic: LoaderUtils.decodeText( new Uint8Array( data.slice( 0, 4 ) ) ),
                        version: headerView.getUint32( 4, true ),
                        length: headerView.getUint32( 8, true )
                };

                if ( this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC ) {

                        throw new Error( 'THREE.GLTFLoader: Unsupported glTF-Binary header.' );

                } else if ( this.header.version < 2.0 ) {

                        throw new Error( 'THREE.GLTFLoader: Legacy binary file detected.' );

                }

                var chunkView = new DataView( data, BINARY_EXTENSION_HEADER_LENGTH );
                var chunkIndex = 0;

                while ( chunkIndex < chunkView.byteLength ) {

                        var chunkLength = chunkView.getUint32( chunkIndex, true );
                        chunkIndex += 4;

                        var chunkType = chunkView.getUint32( chunkIndex, true );
                        chunkIndex += 4;

                        if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON ) {

                                var contentArray = new Uint8Array( data, BINARY_EXTENSION_HEADER_LENGTH + chunkIndex, chunkLength );
                                this.content = LoaderUtils.decodeText( contentArray );

                        } else if ( chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN ) {

                                var byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
                                this.body = data.slice( byteOffset, byteOffset + chunkLength );

                        }

                        // Clients must ignore chunks with unknown types.

                        chunkIndex += chunkLength;

                }

                if ( this.content === null ) {

                        throw new Error( 'THREE.GLTFLoader: JSON content not found.' );

                }

        }

        /**
         * DRACO Mesh Compression Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_draco_mesh_compression
         */
        function GLTFDracoMeshCompressionExtension( json, dracoLoader ) {

                if ( ! dracoLoader ) {

                        throw new Error( 'THREE.GLTFLoader: No DRACOLoader instance provided.' );

                }

                this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
                this.json = json;
                this.dracoLoader = dracoLoader;
                this.dracoLoader.preload();

        }

        GLTFDracoMeshCompressionExtension.prototype.decodePrimitive = function ( primitive, parser ) {

                var json = this.json;
                var dracoLoader = this.dracoLoader;
                var bufferViewIndex = primitive.extensions[ this.name ].bufferView;
                var gltfAttributeMap = primitive.extensions[ this.name ].attributes;
                var threeAttributeMap = {};
                var attributeNormalizedMap = {};
                var attributeTypeMap = {};

                for ( var attributeName in gltfAttributeMap ) {

                        var threeAttributeName = ATTRIBUTES[ attributeName ] || attributeName.toLowerCase();

                        threeAttributeMap[ threeAttributeName ] = gltfAttributeMap[ attributeName ];

                }

                for ( attributeName in primitive.attributes ) {

                        var threeAttributeName = ATTRIBUTES[ attributeName ] || attributeName.toLowerCase();

                        if ( gltfAttributeMap[ attributeName ] !== undefined ) {

                                var accessorDef = json.accessors[ primitive.attributes[ attributeName ] ];
                                var componentType = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];

                                attributeTypeMap[ threeAttributeName ] = componentType;
                                attributeNormalizedMap[ threeAttributeName ] = accessorDef.normalized === true;

                        }

                }

                return parser.getDependency( 'bufferView', bufferViewIndex ).then( function ( bufferView ) {

                        return new Promise( function ( resolve ) {

                                dracoLoader.decodeDracoFile( bufferView, function ( geometry ) {

                                        for ( var attributeName in geometry.attributes ) {

                                                var attribute = geometry.attributes[ attributeName ];
                                                var normalized = attributeNormalizedMap[ attributeName ];

                                                if ( normalized !== undefined ) attribute.normalized = normalized;

                                        }

                                        resolve( geometry );

                                }, threeAttributeMap, attributeTypeMap );

                        } );

                } );

        };

        /**
         * Texture Transform Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_transform
         */
        function GLTFTextureTransformExtension() {

                this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;

        }

        GLTFTextureTransformExtension.prototype.extendTexture = function ( texture, transform ) {

                texture = texture.clone();

                if ( transform.offset !== undefined ) {

                        texture.offset.fromArray( transform.offset );

                }

                if ( transform.rotation !== undefined ) {

                        texture.rotation = transform.rotation;

                }

                if ( transform.scale !== undefined ) {

                        texture.repeat.fromArray( transform.scale );

                }

                if ( transform.texCoord !== undefined ) {

                        console.warn( 'THREE.GLTFLoader: Custom UV sets in "' + this.name + '" extension not yet supported.' );

                }

                texture.needsUpdate = true;

                return texture;

        };

        /**
         * Specular-Glossiness Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
         */

        /**
         * A sub class of StandardMaterial with some of the functionality
         * changed via the `onBeforeCompile` callback
         * @pailhead
         */

        function GLTFMeshStandardSGMaterial( params ) {

                MeshStandardMaterial.call( this );

                this.isGLTFSpecularGlossinessMaterial = true;

                //various chunks that need replacing
                var specularMapParsFragmentChunk = [
                        '#ifdef USE_SPECULARMAP',
                        '       uniform sampler2D specularMap;',
                        '#endif'
                ].join( '\n' );

                var glossinessMapParsFragmentChunk = [
                        '#ifdef USE_GLOSSINESSMAP',
                        '       uniform sampler2D glossinessMap;',
                        '#endif'
                ].join( '\n' );

                var specularMapFragmentChunk = [
                        'vec3 specularFactor = specular;',
                        '#ifdef USE_SPECULARMAP',
                        '       vec4 texelSpecular = texture2D( specularMap, vUv );',
                        '       texelSpecular = sRGBToLinear( texelSpecular );',
                        '       // reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture',
                        '       specularFactor *= texelSpecular.rgb;',
                        '#endif'
                ].join( '\n' );

                var glossinessMapFragmentChunk = [
                        'float glossinessFactor = glossiness;',
                        '#ifdef USE_GLOSSINESSMAP',
                        '       vec4 texelGlossiness = texture2D( glossinessMap, vUv );',
                        '       // reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture',
                        '       glossinessFactor *= texelGlossiness.a;',
                        '#endif'
                ].join( '\n' );

                var lightPhysicalFragmentChunk = [
                        'PhysicalMaterial material;',
                        'material.diffuseColor = diffuseColor.rgb * ( 1. - max( specularFactor.r, max( specularFactor.g, specularFactor.b ) ) );',
                        'vec3 dxy = max( abs( dFdx( geometryNormal ) ), abs( dFdy( geometryNormal ) ) );',
                        'float geometryRoughness = max( max( dxy.x, dxy.y ), dxy.z );',
                        'material.specularRoughness = max( 1.0 - glossinessFactor, 0.0525 ); // 0.0525 corresponds to the base mip of a 256 cubemap.',
                        'material.specularRoughness += geometryRoughness;',
                        'material.specularRoughness = min( material.specularRoughness, 1.0 );',
                        'material.specularColor = specularFactor;',
                ].join( '\n' );

                var uniforms = {
                        specular: { value: new Color().setHex( 0xffffff ) },
                        glossiness: { value: 1 },
                        specularMap: { value: null },
                        glossinessMap: { value: null }
                };

                this._extraUniforms = uniforms;

                this.onBeforeCompile = function ( shader ) {

                        for ( var uniformName in uniforms ) {

                                shader.uniforms[ uniformName ] = uniforms[ uniformName ];

                        }

                        shader.fragmentShader = shader.fragmentShader
                                .replace( 'uniform float roughness;', 'uniform vec3 specular;' )
                                .replace( 'uniform float metalness;', 'uniform float glossiness;' )
                                .replace( '#include <roughnessmap_pars_fragment>', specularMapParsFragmentChunk )
                                .replace( '#include <metalnessmap_pars_fragment>', glossinessMapParsFragmentChunk )
                                .replace( '#include <roughnessmap_fragment>', specularMapFragmentChunk )
                                .replace( '#include <metalnessmap_fragment>', glossinessMapFragmentChunk )
                                .replace( '#include <lights_physical_fragment>', lightPhysicalFragmentChunk );

                };

                Object.defineProperties( this, {

                        specular: {
                                get: function () {

                                        return uniforms.specular.value;

                                },
                                set: function ( v ) {

                                        uniforms.specular.value = v;

                                }
                        },

                        specularMap: {
                                get: function () {

                                        return uniforms.specularMap.value;

                                },
                                set: function ( v ) {

                                        uniforms.specularMap.value = v;

                                        if ( v ) {

                                                this.defines.USE_SPECULARMAP = ''; // USE_UV is set by the renderer for specular maps

                                        } else {

                                                delete this.defines.USE_SPECULARMAP;

                                        }

                                }
                        },

                        glossiness: {
                                get: function () {

                                        return uniforms.glossiness.value;

                                },
                                set: function ( v ) {

                                        uniforms.glossiness.value = v;

                                }
                        },

                        glossinessMap: {
                                get: function () {

                                        return uniforms.glossinessMap.value;

                                },
                                set: function ( v ) {

                                        uniforms.glossinessMap.value = v;

                                        if ( v ) {

                                                this.defines.USE_GLOSSINESSMAP = '';
                                                this.defines.USE_UV = '';

                                        } else {

                                                delete this.defines.USE_GLOSSINESSMAP;
                                                delete this.defines.USE_UV;

                                        }

                                }
                        }

                } );

                delete this.metalness;
                delete this.roughness;
                delete this.metalnessMap;
                delete this.roughnessMap;

                this.setValues( params );

        }

        GLTFMeshStandardSGMaterial.prototype = Object.create( MeshStandardMaterial.prototype );
        GLTFMeshStandardSGMaterial.prototype.constructor = GLTFMeshStandardSGMaterial;

        GLTFMeshStandardSGMaterial.prototype.copy = function ( source ) {

                MeshStandardMaterial.prototype.copy.call( this, source );
                this.specularMap = source.specularMap;
                this.specular.copy( source.specular );
                this.glossinessMap = source.glossinessMap;
                this.glossiness = source.glossiness;
                delete this.metalness;
                delete this.roughness;
                delete this.metalnessMap;
                delete this.roughnessMap;
                return this;

        };

        function GLTFMaterialsPbrSpecularGlossinessExtension() {

                return {

                        name: EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS,

                        specularGlossinessParams: [
                                'color',
                                'map',
                                'lightMap',
                                'lightMapIntensity',
                                'aoMap',
                                'aoMapIntensity',
                                'emissive',
                                'emissiveIntensity',
                                'emissiveMap',
                                'bumpMap',
                                'bumpScale',
                                'normalMap',
                                'normalMapType',
                                'displacementMap',
                                'displacementScale',
                                'displacementBias',
                                'specularMap',
                                'specular',
                                'glossinessMap',
                                'glossiness',
                                'alphaMap',
                                'envMap',
                                'envMapIntensity',
                                'refractionRatio',
                        ],

                        getMaterialType: function () {

                                return GLTFMeshStandardSGMaterial;

                        },

                        extendParams: function ( materialParams, materialDef, parser ) {

                                var pbrSpecularGlossiness = materialDef.extensions[ this.name ];

                                materialParams.color = new Color( 1.0, 1.0, 1.0 );
                                materialParams.opacity = 1.0;

                                var pending = [];

                                if ( Array.isArray( pbrSpecularGlossiness.diffuseFactor ) ) {

                                        var array = pbrSpecularGlossiness.diffuseFactor;

                                        materialParams.color.fromArray( array );
                                        materialParams.opacity = array[ 3 ];

                                }

                                if ( pbrSpecularGlossiness.diffuseTexture !== undefined ) {

                                        pending.push( parser.assignTexture( materialParams, 'map', pbrSpecularGlossiness.diffuseTexture ) );

                                }

                                materialParams.emissive = new Color( 0.0, 0.0, 0.0 );
                                materialParams.glossiness = pbrSpecularGlossiness.glossinessFactor !== undefined ? pbrSpecularGlossiness.glossinessFactor : 1.0;
                                materialParams.specular = new Color( 1.0, 1.0, 1.0 );

                                if ( Array.isArray( pbrSpecularGlossiness.specularFactor ) ) {

                                        materialParams.specular.fromArray( pbrSpecularGlossiness.specularFactor );

                                }

                                if ( pbrSpecularGlossiness.specularGlossinessTexture !== undefined ) {

                                        var specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
                                        pending.push( parser.assignTexture( materialParams, 'glossinessMap', specGlossMapDef ) );
                                        pending.push( parser.assignTexture( materialParams, 'specularMap', specGlossMapDef ) );

                                }

                                return Promise.all( pending );

                        },

                        createMaterial: function ( materialParams ) {

                                var material = new GLTFMeshStandardSGMaterial( materialParams );
                                material.fog = true;

                                material.color = materialParams.color;

                                material.map = materialParams.map === undefined ? null : materialParams.map;

                                material.lightMap = null;
                                material.lightMapIntensity = 1.0;

                                material.aoMap = materialParams.aoMap === undefined ? null : materialParams.aoMap;
                                material.aoMapIntensity = 1.0;

                                material.emissive = materialParams.emissive;
                                material.emissiveIntensity = 1.0;
                                material.emissiveMap = materialParams.emissiveMap === undefined ? null : materialParams.emissiveMap;

                                material.bumpMap = materialParams.bumpMap === undefined ? null : materialParams.bumpMap;
                                material.bumpScale = 1;

                                material.normalMap = materialParams.normalMap === undefined ? null : materialParams.normalMap;
                                material.normalMapType = TangentSpaceNormalMap;

                                if ( materialParams.normalScale ) material.normalScale = materialParams.normalScale;

                                material.displacementMap = null;
                                material.displacementScale = 1;
                                material.displacementBias = 0;

                                material.specularMap = materialParams.specularMap === undefined ? null : materialParams.specularMap;
                                material.specular = materialParams.specular;

                                material.glossinessMap = materialParams.glossinessMap === undefined ? null : materialParams.glossinessMap;
                                material.glossiness = materialParams.glossiness;

                                material.alphaMap = null;

                                material.envMap = materialParams.envMap === undefined ? null : materialParams.envMap;
                                material.envMapIntensity = 1.0;

                                material.refractionRatio = 0.98;

                                return material;

                        },

                };

        }

        /**
         * Mesh Quantization Extension
         *
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization
         */
        function GLTFMeshQuantizationExtension() {

                this.name = EXTENSIONS.KHR_MESH_QUANTIZATION;

        }

        /*********************************/
        /********** INTERPOLATION ********/
        /*********************************/

        // Spline Interpolation
        // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
        function GLTFCubicSplineInterpolant( parameterPositions, sampleValues, sampleSize, resultBuffer ) {

                Interpolant.call( this, parameterPositions, sampleValues, sampleSize, resultBuffer );

        }

        GLTFCubicSplineInterpolant.prototype = Object.create( Interpolant.prototype );
        GLTFCubicSplineInterpolant.prototype.constructor = GLTFCubicSplineInterpolant;

        GLTFCubicSplineInterpolant.prototype.copySampleValue_ = function ( index ) {

                // Copies a sample value to the result buffer. See description of glTF
                // CUBICSPLINE values layout in interpolate_() function below.

                var result = this.resultBuffer,
                        values = this.sampleValues,
                        valueSize = this.valueSize,
                        offset = index * valueSize * 3 + valueSize;

                for ( var i = 0; i !== valueSize; i ++ ) {

                        result[ i ] = values[ offset + i ];

                }

                return result;

        };

        GLTFCubicSplineInterpolant.prototype.beforeStart_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

        GLTFCubicSplineInterpolant.prototype.afterEnd_ = GLTFCubicSplineInterpolant.prototype.copySampleValue_;

        GLTFCubicSplineInterpolant.prototype.interpolate_ = function ( i1, t0, t, t1 ) {

                var result = this.resultBuffer;
                var values = this.sampleValues;
                var stride = this.valueSize;

                var stride2 = stride * 2;
                var stride3 = stride * 3;

                var td = t1 - t0;

                var p = ( t - t0 ) / td;
                var pp = p * p;
                var ppp = pp * p;

                var offset1 = i1 * stride3;
                var offset0 = offset1 - stride3;

                var s2 = - 2 * ppp + 3 * pp;
                var s3 = ppp - pp;
                var s0 = 1 - s2;
                var s1 = s3 - pp + p;

                // Layout of keyframe output values for CUBICSPLINE animations:
                //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
                for ( var i = 0; i !== stride; i ++ ) {

                        var p0 = values[ offset0 + i + stride ]; // splineVertex_k
                        var m0 = values[ offset0 + i + stride2 ] * td; // outTangent_k * (t_k+1 - t_k)
                        var p1 = values[ offset1 + i + stride ]; // splineVertex_k+1
                        var m1 = values[ offset1 + i ] * td; // inTangent_k+1 * (t_k+1 - t_k)

                        result[ i ] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;

                }

                return result;

        };

        /*********************************/
        /********** INTERNALS ************/
        /*********************************/

        /* CONSTANTS */

        var WEBGL_CONSTANTS = {
                FLOAT: 5126,
                //FLOAT_MAT2: 35674,
                FLOAT_MAT3: 35675,
                FLOAT_MAT4: 35676,
                FLOAT_VEC2: 35664,
                FLOAT_VEC3: 35665,
                FLOAT_VEC4: 35666,
                LINEAR: 9729,
                REPEAT: 10497,
                SAMPLER_2D: 35678,
                POINTS: 0,
                LINES: 1,
                LINE_LOOP: 2,
                LINE_STRIP: 3,
                TRIANGLES: 4,
                TRIANGLE_STRIP: 5,
                TRIANGLE_FAN: 6,
                UNSIGNED_BYTE: 5121,
                UNSIGNED_SHORT: 5123
        };

        var WEBGL_COMPONENT_TYPES = {
                5120: Int8Array,
                5121: Uint8Array,
                5122: Int16Array,
                5123: Uint16Array,
                5125: Uint32Array,
                5126: Float32Array
        };

        var WEBGL_FILTERS = {
                9728: NearestFilter,
                9729: LinearFilter,
                9984: NearestMipmapNearestFilter,
                9985: LinearMipmapNearestFilter,
                9986: NearestMipmapLinearFilter,
                9987: LinearMipmapLinearFilter
        };

        var WEBGL_WRAPPINGS = {
                33071: ClampToEdgeWrapping,
                33648: MirroredRepeatWrapping,
                10497: RepeatWrapping
        };

        var WEBGL_TYPE_SIZES = {
                'SCALAR': 1,
                'VEC2': 2,
                'VEC3': 3,
                'VEC4': 4,
                'MAT2': 4,
                'MAT3': 9,
                'MAT4': 16
        };

        var ATTRIBUTES = {
                POSITION: 'position',
                NORMAL: 'normal',
                TANGENT: 'tangent',
                TEXCOORD_0: 'uv',
                TEXCOORD_1: 'uv2',
                COLOR_0: 'color',
                WEIGHTS_0: 'skinWeight',
                JOINTS_0: 'skinIndex',
        };

        var PATH_PROPERTIES = {
                scale: 'scale',
                translation: 'position',
                rotation: 'quaternion',
                weights: 'morphTargetInfluences'
        };

        var INTERPOLATION = {
                CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
                                        // keyframe track will be initialized with a default interpolation type, then modified.
                LINEAR: InterpolateLinear,
                STEP: InterpolateDiscrete
        };

        var ALPHA_MODES = {
                OPAQUE: 'OPAQUE',
                MASK: 'MASK',
                BLEND: 'BLEND'
        };

        /* UTILITY FUNCTIONS */

        function resolveURL( url, path ) {

                // Invalid URL
                if ( typeof url !== 'string' || url === '' ) return '';

                // Host Relative URL
                if ( /^https?:\/\//i.test( path ) && /^\//.test( url ) ) {

                        path = path.replace( /(^https?:\/\/[^\/]+).*/i, '$1' );

                }

                // Absolute URL http://,https://,//
                if ( /^(https?:)?\/\//i.test( url ) ) return url;

                // Data URI
                if ( /^data:.*,.*$/i.test( url ) ) return url;

                // Blob URL
                if ( /^blob:.*$/i.test( url ) ) return url;

                // Relative URL
                return path + url;

        }

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
         */
        function createDefaultMaterial( cache ) {

                if ( cache[ 'DefaultMaterial' ] === undefined ) {

                        cache[ 'DefaultMaterial' ] = new MeshStandardMaterial( {
                                color: 0xFFFFFF,
                                emissive: 0x000000,
                                metalness: 1,
                                roughness: 1,
                                transparent: false,
                                depthTest: true,
                                side: FrontSide
                        } );

                }

                return cache[ 'DefaultMaterial' ];

        }

        function addUnknownExtensionsToUserData( knownExtensions, object, objectDef ) {

                // Add unknown glTF extensions to an object's userData.

                for ( var name in objectDef.extensions ) {

                        if ( knownExtensions[ name ] === undefined ) {

                                object.userData.gltfExtensions = object.userData.gltfExtensions || {};
                                object.userData.gltfExtensions[ name ] = objectDef.extensions[ name ];

                        }

                }

        }

        /**
         * @param {Object3D|Material|BufferGeometry} object
         * @param {GLTF.definition} gltfDef
         */
        function assignExtrasToUserData( object, gltfDef ) {

                if ( gltfDef.extras !== undefined ) {

                        if ( typeof gltfDef.extras === 'object' ) {

                                Object.assign( object.userData, gltfDef.extras );

                        } else {

                                console.warn( 'THREE.GLTFLoader: Ignoring primitive type .extras, ' + gltfDef.extras );

                        }

                }

        }

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
         *
         * @param {BufferGeometry} geometry
         * @param {Array<GLTF.Target>} targets
         * @param {GLTFParser} parser
         * @return {Promise<BufferGeometry>}
         */
        function addMorphTargets( geometry, targets, parser ) {

                var hasMorphPosition = false;
                var hasMorphNormal = false;

                for ( var i = 0, il = targets.length; i < il; i ++ ) {

                        var target = targets[ i ];

                        if ( target.POSITION !== undefined ) hasMorphPosition = true;
                        if ( target.NORMAL !== undefined ) hasMorphNormal = true;

                        if ( hasMorphPosition && hasMorphNormal ) break;

                }

                if ( ! hasMorphPosition && ! hasMorphNormal ) return Promise.resolve( geometry );

                var pendingPositionAccessors = [];
                var pendingNormalAccessors = [];

                for ( var i = 0, il = targets.length; i < il; i ++ ) {

                        var target = targets[ i ];

                        if ( hasMorphPosition ) {

                                var pendingAccessor = target.POSITION !== undefined
                                        ? parser.getDependency( 'accessor', target.POSITION )
                                        : geometry.attributes.position;

                                pendingPositionAccessors.push( pendingAccessor );

                        }

                        if ( hasMorphNormal ) {

                                var pendingAccessor = target.NORMAL !== undefined
                                        ? parser.getDependency( 'accessor', target.NORMAL )
                                        : geometry.attributes.normal;

                                pendingNormalAccessors.push( pendingAccessor );

                        }

                }

                return Promise.all( [
                        Promise.all( pendingPositionAccessors ),
                        Promise.all( pendingNormalAccessors )
                ] ).then( function ( accessors ) {

                        var morphPositions = accessors[ 0 ];
                        var morphNormals = accessors[ 1 ];

                        if ( hasMorphPosition ) geometry.morphAttributes.position = morphPositions;
                        if ( hasMorphNormal ) geometry.morphAttributes.normal = morphNormals;
                        geometry.morphTargetsRelative = true;

                        return geometry;

                } );

        }

        /**
         * @param {Mesh} mesh
         * @param {GLTF.Mesh} meshDef
         */
        function updateMorphTargets( mesh, meshDef ) {

                mesh.updateMorphTargets();

                if ( meshDef.weights !== undefined ) {

                        for ( var i = 0, il = meshDef.weights.length; i < il; i ++ ) {

                                mesh.morphTargetInfluences[ i ] = meshDef.weights[ i ];

                        }

                }

                // .extras has user-defined data, so check that .extras.targetNames is an array.
                if ( meshDef.extras && Array.isArray( meshDef.extras.targetNames ) ) {

                        var targetNames = meshDef.extras.targetNames;

                        if ( mesh.morphTargetInfluences.length === targetNames.length ) {

                                mesh.morphTargetDictionary = {};

                                for ( var i = 0, il = targetNames.length; i < il; i ++ ) {

                                        mesh.morphTargetDictionary[ targetNames[ i ] ] = i;

                                }

                        } else {

                                console.warn( 'THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names.' );

                        }

                }

        }

        function createPrimitiveKey( primitiveDef ) {

                var dracoExtension = primitiveDef.extensions && primitiveDef.extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ];
                var geometryKey;

                if ( dracoExtension ) {

                        geometryKey = 'draco:' + dracoExtension.bufferView
                                + ':' + dracoExtension.indices
                                + ':' + createAttributesKey( dracoExtension.attributes );

                } else {

                        geometryKey = primitiveDef.indices + ':' + createAttributesKey( primitiveDef.attributes ) + ':' + primitiveDef.mode;

                }

                return geometryKey;

        }

        function createAttributesKey( attributes ) {

                var attributesKey = '';

                var keys = Object.keys( attributes ).sort();

                for ( var i = 0, il = keys.length; i < il; i ++ ) {

                        attributesKey += keys[ i ] + ':' + attributes[ keys[ i ] ] + ';';

                }

                return attributesKey;

        }

        /* GLTF PARSER */

        function GLTFParser( json, options ) {

                this.json = json || {};
                this.extensions = {};
                this.plugins = {};
                this.options = options || {};

                // loader object cache
                this.cache = new GLTFRegistry();

                // associations between Three.js objects and glTF elements
                this.associations = new Map();

                // BufferGeometry caching
                this.primitiveCache = {};

                // Object3D instance caches
                this.meshCache = { refs: {}, uses: {} };
                this.cameraCache = { refs: {}, uses: {} };
                this.lightCache = { refs: {}, uses: {} };

                // Track node names, to ensure no duplicates
                this.nodeNamesUsed = {};

                // Use an ImageBitmapLoader if imageBitmaps are supported. Moves much of the
                // expensive work of uploading a texture to the GPU off the main thread.
                if ( typeof createImageBitmap !== 'undefined' && /Firefox/.test( navigator.userAgent ) === false ) {

                        this.textureLoader = new ImageBitmapLoader( this.options.manager );

                } else {

                        this.textureLoader = new TextureLoader( this.options.manager );

                }

                this.textureLoader.setCrossOrigin( this.options.crossOrigin );

                this.fileLoader = new FileLoader( this.options.manager );
                this.fileLoader.setResponseType( 'arraybuffer' );

                if ( this.options.crossOrigin === 'use-credentials' ) {

                        this.fileLoader.setWithCredentials( true );

                }

        }

        GLTFParser.prototype.setExtensions = function ( extensions ) {

                this.extensions = extensions;

        };

        GLTFParser.prototype.setPlugins = function ( plugins ) {

                this.plugins = plugins;

        };

        GLTFParser.prototype.parse = function ( onLoad, onError ) {

                var parser = this;
                var json = this.json;
                var extensions = this.extensions;

                // Clear the loader cache
                this.cache.removeAll();

                // Mark the special nodes/meshes in json for efficient parse
                this._invokeAll( function ( ext ) {

                        return ext._markDefs && ext._markDefs();

                } );

                Promise.all( [

                        this.getDependencies( 'scene' ),
                        this.getDependencies( 'animation' ),
                        this.getDependencies( 'camera' ),

                ] ).then( function ( dependencies ) {

                        var result = {
                                scene: dependencies[ 0 ][ json.scene || 0 ],
                                scenes: dependencies[ 0 ],
                                animations: dependencies[ 1 ],
                                cameras: dependencies[ 2 ],
                                asset: json.asset,
                                parser: parser,
                                userData: {}
                        };

                        addUnknownExtensionsToUserData( extensions, result, json );

                        assignExtrasToUserData( result, json );

                        onLoad( result );

                } ).catch( onError );

        };

        /**
         * Marks the special nodes/meshes in json for efficient parse.
         */
        GLTFParser.prototype._markDefs = function () {

                var nodeDefs = this.json.nodes || [];
                var skinDefs = this.json.skins || [];
                var meshDefs = this.json.meshes || [];

                // Nothing in the node definition indicates whether it is a Bone or an
                // Object3D. Use the skins' joint references to mark bones.
                for ( var skinIndex = 0, skinLength = skinDefs.length; skinIndex < skinLength; skinIndex ++ ) {

                        var joints = skinDefs[ skinIndex ].joints;

                        for ( var i = 0, il = joints.length; i < il; i ++ ) {

                                nodeDefs[ joints[ i ] ].isBone = true;

                        }

                }

                // Iterate over all nodes, marking references to shared resources,
                // as well as skeleton joints.
                for ( var nodeIndex = 0, nodeLength = nodeDefs.length; nodeIndex < nodeLength; nodeIndex ++ ) {

                        var nodeDef = nodeDefs[ nodeIndex ];

                        if ( nodeDef.mesh !== undefined ) {

                                this._addNodeRef( this.meshCache, nodeDef.mesh );

                                // Nothing in the mesh definition indicates whether it is
                                // a SkinnedMesh or Mesh. Use the node's mesh reference
                                // to mark SkinnedMesh if node has skin.
                                if ( nodeDef.skin !== undefined ) {

                                        meshDefs[ nodeDef.mesh ].isSkinnedMesh = true;

                                }

                        }

                        if ( nodeDef.camera !== undefined ) {

                                this._addNodeRef( this.cameraCache, nodeDef.camera );

                        }

                }

        };

        /**
         * Counts references to shared node / Object3D resources. These resources
         * can be reused, or "instantiated", at multiple nodes in the scene
         * hierarchy. Mesh, Camera, and Light instances are instantiated and must
         * be marked. Non-scenegraph resources (like Materials, Geometries, and
         * Textures) can be reused directly and are not marked here.
         *
         * Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
         */
        GLTFParser.prototype._addNodeRef = function ( cache, index ) {

                if ( index === undefined ) return;

                if ( cache.refs[ index ] === undefined ) {

                        cache.refs[ index ] = cache.uses[ index ] = 0;

                }

                cache.refs[ index ] ++;

        };

        /** Returns a reference to a shared resource, cloning it if necessary. */
        GLTFParser.prototype._getNodeRef = function ( cache, index, object ) {

                if ( cache.refs[ index ] <= 1 ) return object;

                var ref = object.clone();

                ref.name += '_instance_' + ( cache.uses[ index ] ++ );

                return ref;

        };

        GLTFParser.prototype._invokeOne = function ( func ) {

                var extensions = Object.values( this.plugins );
                extensions.push( this );

                for ( var i = 0; i < extensions.length; i ++ ) {

                        var result = func( extensions[ i ] );

                        if ( result ) return result;

                }

        };

        GLTFParser.prototype._invokeAll = function ( func ) {

                var extensions = Object.values( this.plugins );
                extensions.unshift( this );

                var pending = [];

                for ( var i = 0; i < extensions.length; i ++ ) {

                        var result = func( extensions[ i ] );

                        if ( result ) pending.push( result );

                }

                return pending;

        };

        /**
         * Requests the specified dependency asynchronously, with caching.
         * @param {string} type
         * @param {number} index
         * @return {Promise<Object3D|Material|THREE.Texture|AnimationClip|ArrayBuffer|Object>}
         */
        GLTFParser.prototype.getDependency = function ( type, index ) {

                var cacheKey = type + ':' + index;
                var dependency = this.cache.get( cacheKey );

                if ( ! dependency ) {

                        switch ( type ) {

                                case 'scene':
                                        dependency = this.loadScene( index );
                                        break;

                                case 'node':
                                        dependency = this.loadNode( index );
                                        break;

                                case 'mesh':
                                        dependency = this._invokeOne( function ( ext ) {

                                                return ext.loadMesh && ext.loadMesh( index );

                                        } );
                                        break;

                                case 'accessor':
                                        dependency = this.loadAccessor( index );
                                        break;

                                case 'bufferView':
                                        dependency = this._invokeOne( function ( ext ) {

                                                return ext.loadBufferView && ext.loadBufferView( index );

                                        } );
                                        break;

                                case 'buffer':
                                        dependency = this.loadBuffer( index );
                                        break;

                                case 'material':
                                        dependency = this._invokeOne( function ( ext ) {

                                                return ext.loadMaterial && ext.loadMaterial( index );

                                        } );
                                        break;

                                case 'texture':
                                        dependency = this._invokeOne( function ( ext ) {

                                                return ext.loadTexture && ext.loadTexture( index );

                                        } );
                                        break;

                                case 'skin':
                                        dependency = this.loadSkin( index );
                                        break;

                                case 'animation':
                                        dependency = this.loadAnimation( index );
                                        break;

                                case 'camera':
                                        dependency = this.loadCamera( index );
                                        break;

                                default:
                                        throw new Error( 'Unknown type: ' + type );

                        }

                        this.cache.add( cacheKey, dependency );

                }

                return dependency;

        };

        /**
         * Requests all dependencies of the specified type asynchronously, with caching.
         * @param {string} type
         * @return {Promise<Array<Object>>}
         */
        GLTFParser.prototype.getDependencies = function ( type ) {

                var dependencies = this.cache.get( type );

                if ( ! dependencies ) {

                        var parser = this;
                        var defs = this.json[ type + ( type === 'mesh' ? 'es' : 's' ) ] || [];

                        dependencies = Promise.all( defs.map( function ( def, index ) {

                                return parser.getDependency( type, index );

                        } ) );

                        this.cache.add( type, dependencies );

                }

                return dependencies;

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
         * @param {number} bufferIndex
         * @return {Promise<ArrayBuffer>}
         */
        GLTFParser.prototype.loadBuffer = function ( bufferIndex ) {

                var bufferDef = this.json.buffers[ bufferIndex ];
                var loader = this.fileLoader;

                if ( bufferDef.type && bufferDef.type !== 'arraybuffer' ) {

                        throw new Error( 'THREE.GLTFLoader: ' + bufferDef.type + ' buffer type is not supported.' );

                }

                // If present, GLB container is required to be the first buffer.
                if ( bufferDef.uri === undefined && bufferIndex === 0 ) {

                        return Promise.resolve( this.extensions[ EXTENSIONS.KHR_BINARY_GLTF ].body );

                }

                var options = this.options;

                return new Promise( function ( resolve, reject ) {

                        loader.load( resolveURL( bufferDef.uri, options.path ), resolve, undefined, function () {

                                reject( new Error( 'THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".' ) );

                        } );

                } );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
         * @param {number} bufferViewIndex
         * @return {Promise<ArrayBuffer>}
         */
        GLTFParser.prototype.loadBufferView = function ( bufferViewIndex ) {

                var bufferViewDef = this.json.bufferViews[ bufferViewIndex ];

                return this.getDependency( 'buffer', bufferViewDef.buffer ).then( function ( buffer ) {

                        var byteLength = bufferViewDef.byteLength || 0;
                        var byteOffset = bufferViewDef.byteOffset || 0;
                        return buffer.slice( byteOffset, byteOffset + byteLength );

                } );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
         * @param {number} accessorIndex
         * @return {Promise<BufferAttribute|InterleavedBufferAttribute>}
         */
        GLTFParser.prototype.loadAccessor = function ( accessorIndex ) {

                var parser = this;
                var json = this.json;

                var accessorDef = this.json.accessors[ accessorIndex ];

                if ( accessorDef.bufferView === undefined && accessorDef.sparse === undefined ) {

                        // Ignore empty accessors, which may be used to declare runtime
                        // information about attributes coming from another source (e.g. Draco
                        // compression extension).
                        return Promise.resolve( null );

                }

                var pendingBufferViews = [];

                if ( accessorDef.bufferView !== undefined ) {

                        pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.bufferView ) );

                } else {

                        pendingBufferViews.push( null );

                }

                if ( accessorDef.sparse !== undefined ) {

                        pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.sparse.indices.bufferView ) );
                        pendingBufferViews.push( this.getDependency( 'bufferView', accessorDef.sparse.values.bufferView ) );

                }

                return Promise.all( pendingBufferViews ).then( function ( bufferViews ) {

                        var bufferView = bufferViews[ 0 ];

                        var itemSize = WEBGL_TYPE_SIZES[ accessorDef.type ];
                        var TypedArray = WEBGL_COMPONENT_TYPES[ accessorDef.componentType ];

                        // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
                        var elementBytes = TypedArray.BYTES_PER_ELEMENT;
                        var itemBytes = elementBytes * itemSize;
                        var byteOffset = accessorDef.byteOffset || 0;
                        var byteStride = accessorDef.bufferView !== undefined ? json.bufferViews[ accessorDef.bufferView ].byteStride : undefined;
                        var normalized = accessorDef.normalized === true;
                        var array, bufferAttribute;

                        // The buffer is not interleaved if the stride is the item size in bytes.
                        if ( byteStride && byteStride !== itemBytes ) {

                                // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
                                // This makes sure that IBA.count reflects accessor.count properly
                                var ibSlice = Math.floor( byteOffset / byteStride );
                                var ibCacheKey = 'InterleavedBuffer:' + accessorDef.bufferView + ':' + accessorDef.componentType + ':' + ibSlice + ':' + accessorDef.count;
                                var ib = parser.cache.get( ibCacheKey );

                                if ( ! ib ) {

                                        array = new TypedArray( bufferView, ibSlice * byteStride, accessorDef.count * byteStride / elementBytes );

                                        // Integer parameters to IB/IBA are in array elements, not bytes.
                                        ib = new InterleavedBuffer( array, byteStride / elementBytes );

                                        parser.cache.add( ibCacheKey, ib );

                                }

                                bufferAttribute = new InterleavedBufferAttribute( ib, itemSize, ( byteOffset % byteStride ) / elementBytes, normalized );

                        } else {

                                if ( bufferView === null ) {

                                        array = new TypedArray( accessorDef.count * itemSize );

                                } else {

                                        array = new TypedArray( bufferView, byteOffset, accessorDef.count * itemSize );

                                }

                                bufferAttribute = new BufferAttribute( array, itemSize, normalized );

                        }

                        // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
                        if ( accessorDef.sparse !== undefined ) {

                                var itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
                                var TypedArrayIndices = WEBGL_COMPONENT_TYPES[ accessorDef.sparse.indices.componentType ];

                                var byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
                                var byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;

                                var sparseIndices = new TypedArrayIndices( bufferViews[ 1 ], byteOffsetIndices, accessorDef.sparse.count * itemSizeIndices );
                                var sparseValues = new TypedArray( bufferViews[ 2 ], byteOffsetValues, accessorDef.sparse.count * itemSize );

                                if ( bufferView !== null ) {

                                        // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
                                        bufferAttribute = new BufferAttribute( bufferAttribute.array.slice(), bufferAttribute.itemSize, bufferAttribute.normalized );

                                }

                                for ( var i = 0, il = sparseIndices.length; i < il; i ++ ) {

                                        var index = sparseIndices[ i ];

                                        bufferAttribute.setX( index, sparseValues[ i * itemSize ] );
                                        if ( itemSize >= 2 ) bufferAttribute.setY( index, sparseValues[ i * itemSize + 1 ] );
                                        if ( itemSize >= 3 ) bufferAttribute.setZ( index, sparseValues[ i * itemSize + 2 ] );
                                        if ( itemSize >= 4 ) bufferAttribute.setW( index, sparseValues[ i * itemSize + 3 ] );
                                        if ( itemSize >= 5 ) throw new Error( 'THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute.' );

                                }

                        }

                        return bufferAttribute;

                } );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
         * @param {number} textureIndex
         * @return {Promise<THREE.Texture>}
         */
        GLTFParser.prototype.loadTexture = function ( textureIndex ) {

                var parser = this;
                var json = this.json;
                var options = this.options;

                var textureDef = json.textures[ textureIndex ];

                var textureExtensions = textureDef.extensions || {};

                var source;

                if ( textureExtensions[ EXTENSIONS.MSFT_TEXTURE_DDS ] ) {

                        source = json.images[ textureExtensions[ EXTENSIONS.MSFT_TEXTURE_DDS ].source ];

                } else {

                        source = json.images[ textureDef.source ];

                }

                var loader;

                if ( source.uri ) {

                        loader = options.manager.getHandler( source.uri );

                }

                if ( ! loader ) {

                        loader = textureExtensions[ EXTENSIONS.MSFT_TEXTURE_DDS ]
                                ? parser.extensions[ EXTENSIONS.MSFT_TEXTURE_DDS ].ddsLoader
                                : this.textureLoader;

                }

                return this.loadTextureImage( textureIndex, source, loader );

        };

        GLTFParser.prototype.loadTextureImage = function ( textureIndex, source, loader ) {

                var parser = this;
                var json = this.json;
                var options = this.options;

                var textureDef = json.textures[ textureIndex ];

                var URL = self.URL || self.webkitURL;

                var sourceURI = source.uri;
                var isObjectURL = false;
                var hasAlpha = true;

                if ( source.mimeType === 'image/jpeg' ) hasAlpha = false;

                if ( source.bufferView !== undefined ) {

                        // Load binary image data from bufferView, if provided.

                        sourceURI = parser.getDependency( 'bufferView', source.bufferView ).then( function ( bufferView ) {

                                if ( source.mimeType === 'image/png' ) {

                                        // Inspect the PNG 'IHDR' chunk to determine whether the image could have an
                                        // alpha channel. This check is conservative — the image could have an alpha
                                        // channel with all values == 1, and the indexed type (colorType == 3) only
                                        // sometimes contains alpha.
                                        //
                                        // https://en.wikipedia.org/wiki/Portable_Network_Graphics#File_header
                                        var colorType = new DataView( bufferView, 25, 1 ).getUint8( 0, false );
                                        hasAlpha = colorType === 6 || colorType === 4 || colorType === 3;

                                }

                                isObjectURL = true;
                                var blob = new Blob( [ bufferView ], { type: source.mimeType } );
                                sourceURI = URL.createObjectURL( blob );
                                return sourceURI;

                        } );

                }

                return Promise.resolve( sourceURI ).then( function ( sourceURI ) {

                        return new Promise( function ( resolve, reject ) {

                                var onLoad = resolve;

                                if ( loader.isImageBitmapLoader === true ) {

                                        onLoad = function ( imageBitmap ) {

                                                resolve( new CanvasTexture( imageBitmap ) );

                                        };

                                }

                                loader.load( resolveURL( sourceURI, options.path ), onLoad, undefined, reject );

                        } );

                } ).then( function ( texture ) {

                        // Clean up resources and configure Texture.

                        if ( isObjectURL === true ) {

                                URL.revokeObjectURL( sourceURI );

                        }

                        texture.flipY = false;

                        if ( textureDef.name ) texture.name = textureDef.name;

                        // When there is definitely no alpha channel in the texture, set RGBFormat to save space.
                        if ( ! hasAlpha ) texture.format = RGBFormat;

                        var samplers = json.samplers || {};
                        var sampler = samplers[ textureDef.sampler ] || {};

                        texture.magFilter = WEBGL_FILTERS[ sampler.magFilter ] || LinearFilter;
                        texture.minFilter = WEBGL_FILTERS[ sampler.minFilter ] || LinearMipmapLinearFilter;
                        texture.wrapS = WEBGL_WRAPPINGS[ sampler.wrapS ] || RepeatWrapping;
                        texture.wrapT = WEBGL_WRAPPINGS[ sampler.wrapT ] || RepeatWrapping;

                        parser.associations.set( texture, {
                                type: 'textures',
                                index: textureIndex
                        } );

                        return texture;

                } );

        };

        /**
         * Asynchronously assigns a texture to the given material parameters.
         * @param {Object} materialParams
         * @param {string} mapName
         * @param {Object} mapDef
         * @return {Promise}
         */
        GLTFParser.prototype.assignTexture = function ( materialParams, mapName, mapDef ) {

                var parser = this;

                return this.getDependency( 'texture', mapDef.index ).then( function ( texture ) {

                        // Materials sample aoMap from UV set 1 and other maps from UV set 0 - this can't be configured
                        // However, we will copy UV set 0 to UV set 1 on demand for aoMap
                        if ( mapDef.texCoord !== undefined && mapDef.texCoord != 0 && ! ( mapName === 'aoMap' && mapDef.texCoord == 1 ) ) {

                                console.warn( 'THREE.GLTFLoader: Custom UV set ' + mapDef.texCoord + ' for texture ' + mapName + ' not yet supported.' );

                        }

                        if ( parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] ) {

                                var transform = mapDef.extensions !== undefined ? mapDef.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ] : undefined;

                                if ( transform ) {

                                        var gltfReference = parser.associations.get( texture );
                                        texture = parser.extensions[ EXTENSIONS.KHR_TEXTURE_TRANSFORM ].extendTexture( texture, transform );
                                        parser.associations.set( texture, gltfReference );

                                }

                        }

                        materialParams[ mapName ] = texture;

                } );

        };

        /**
         * Assigns final material to a Mesh, Line, or Points instance. The instance
         * already has a material (generated from the glTF material options alone)
         * but reuse of the same glTF material may require multiple threejs materials
         * to accomodate different primitive types, defines, etc. New materials will
         * be created if necessary, and reused from a cache.
         * @param  {Object3D} mesh Mesh, Line, or Points instance.
         */
        GLTFParser.prototype.assignFinalMaterial = function ( mesh ) {

                var geometry = mesh.geometry;
                var material = mesh.material;

                var useVertexTangents = geometry.attributes.tangent !== undefined;
                var useVertexColors = geometry.attributes.color !== undefined;
                var useFlatShading = geometry.attributes.normal === undefined;
                var useSkinning = mesh.isSkinnedMesh === true;
                var useMorphTargets = Object.keys( geometry.morphAttributes ).length > 0;
                var useMorphNormals = useMorphTargets && geometry.morphAttributes.normal !== undefined;

                if ( mesh.isPoints ) {

                        var cacheKey = 'PointsMaterial:' + material.uuid;

                        var pointsMaterial = this.cache.get( cacheKey );

                        if ( ! pointsMaterial ) {

                                pointsMaterial = new PointsMaterial();
                                Material.prototype.copy.call( pointsMaterial, material );
                                pointsMaterial.color.copy( material.color );
                                pointsMaterial.map = material.map;
                                pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px

                                this.cache.add( cacheKey, pointsMaterial );

                        }

                        material = pointsMaterial;

                } else if ( mesh.isLine ) {

                        var cacheKey = 'LineBasicMaterial:' + material.uuid;

                        var lineMaterial = this.cache.get( cacheKey );

                        if ( ! lineMaterial ) {

                                lineMaterial = new LineBasicMaterial();
                                Material.prototype.copy.call( lineMaterial, material );
                                lineMaterial.color.copy( material.color );

                                this.cache.add( cacheKey, lineMaterial );

                        }

                        material = lineMaterial;

                }

                // Clone the material if it will be modified
                if ( useVertexTangents || useVertexColors || useFlatShading || useSkinning || useMorphTargets ) {

                        var cacheKey = 'ClonedMaterial:' + material.uuid + ':';

                        if ( material.isGLTFSpecularGlossinessMaterial ) cacheKey += 'specular-glossiness:';
                        if ( useSkinning ) cacheKey += 'skinning:';
                        if ( useVertexTangents ) cacheKey += 'vertex-tangents:';
                        if ( useVertexColors ) cacheKey += 'vertex-colors:';
                        if ( useFlatShading ) cacheKey += 'flat-shading:';
                        if ( useMorphTargets ) cacheKey += 'morph-targets:';
                        if ( useMorphNormals ) cacheKey += 'morph-normals:';

                        var cachedMaterial = this.cache.get( cacheKey );

                        if ( ! cachedMaterial ) {

                                cachedMaterial = material.clone();

                                if ( useSkinning ) cachedMaterial.skinning = true;
                                if ( useVertexTangents ) cachedMaterial.vertexTangents = true;
                                if ( useVertexColors ) cachedMaterial.vertexColors = true;
                                if ( useFlatShading ) cachedMaterial.flatShading = true;
                                if ( useMorphTargets ) cachedMaterial.morphTargets = true;
                                if ( useMorphNormals ) cachedMaterial.morphNormals = true;

                                this.cache.add( cacheKey, cachedMaterial );

                                this.associations.set( cachedMaterial, this.associations.get( material ) );

                        }

                        material = cachedMaterial;

                }

                // workarounds for mesh and geometry

                if ( material.aoMap && geometry.attributes.uv2 === undefined && geometry.attributes.uv !== undefined ) {

                        geometry.setAttribute( 'uv2', geometry.attributes.uv );

                }

                // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
                if ( material.normalScale && ! useVertexTangents ) {

                        material.normalScale.y = - material.normalScale.y;

                }

                if ( material.clearcoatNormalScale && ! useVertexTangents ) {

                        material.clearcoatNormalScale.y = - material.clearcoatNormalScale.y;

                }

                mesh.material = material;

        };

        GLTFParser.prototype.getMaterialType = function ( /* materialIndex */ ) {

                return MeshStandardMaterial;

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
         * @param {number} materialIndex
         * @return {Promise<Material>}
         */
        GLTFParser.prototype.loadMaterial = function ( materialIndex ) {

                var parser = this;
                var json = this.json;
                var extensions = this.extensions;
                var materialDef = json.materials[ materialIndex ];

                var materialType;
                var materialParams = {};
                var materialExtensions = materialDef.extensions || {};

                var pending = [];

                if ( materialExtensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ] ) {

                        var sgExtension = extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ];
                        materialType = sgExtension.getMaterialType();
                        pending.push( sgExtension.extendParams( materialParams, materialDef, parser ) );

                } else if ( materialExtensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ] ) {

                        var kmuExtension = extensions[ EXTENSIONS.KHR_MATERIALS_UNLIT ];
                        materialType = kmuExtension.getMaterialType();
                        pending.push( kmuExtension.extendParams( materialParams, materialDef, parser ) );

                } else {

                        // Specification:
                        // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

                        var metallicRoughness = materialDef.pbrMetallicRoughness || {};

                        materialParams.color = new Color( 1.0, 1.0, 1.0 );
                        materialParams.opacity = 1.0;

                        if ( Array.isArray( metallicRoughness.baseColorFactor ) ) {

                                var array = metallicRoughness.baseColorFactor;

                                materialParams.color.fromArray( array );
                                materialParams.opacity = array[ 3 ];

                        }

                        if ( metallicRoughness.baseColorTexture !== undefined ) {

                                pending.push( parser.assignTexture( materialParams, 'map', metallicRoughness.baseColorTexture ) );

                        }

                        materialParams.metalness = metallicRoughness.metallicFactor !== undefined ? metallicRoughness.metallicFactor : 1.0;
                        materialParams.roughness = metallicRoughness.roughnessFactor !== undefined ? metallicRoughness.roughnessFactor : 1.0;

                        if ( metallicRoughness.metallicRoughnessTexture !== undefined ) {

                                pending.push( parser.assignTexture( materialParams, 'metalnessMap', metallicRoughness.metallicRoughnessTexture ) );
                                pending.push( parser.assignTexture( materialParams, 'roughnessMap', metallicRoughness.metallicRoughnessTexture ) );

                        }

                        materialType = this._invokeOne( function ( ext ) {

                                return ext.getMaterialType && ext.getMaterialType( materialIndex );

                        } );

                        pending.push( Promise.all( this._invokeAll( function ( ext ) {

                                return ext.extendMaterialParams && ext.extendMaterialParams( materialIndex, materialParams );

                        } ) ) );

                }

                if ( materialDef.doubleSided === true ) {

                        materialParams.side = DoubleSide;

                }

                var alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;

                if ( alphaMode === ALPHA_MODES.BLEND ) {

                        materialParams.transparent = true;

                        // See: https://github.com/mrdoob/three.js/issues/17706
                        materialParams.depthWrite = false;

                } else {

                        materialParams.transparent = false;

                        if ( alphaMode === ALPHA_MODES.MASK ) {

                                materialParams.alphaTest = materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;

                        }

                }

                if ( materialDef.normalTexture !== undefined && materialType !== MeshBasicMaterial ) {

                        pending.push( parser.assignTexture( materialParams, 'normalMap', materialDef.normalTexture ) );

                        materialParams.normalScale = new Vector2( 1, 1 );

                        if ( materialDef.normalTexture.scale !== undefined ) {

                                materialParams.normalScale.set( materialDef.normalTexture.scale, materialDef.normalTexture.scale );

                        }

                }

                if ( materialDef.occlusionTexture !== undefined && materialType !== MeshBasicMaterial ) {

                        pending.push( parser.assignTexture( materialParams, 'aoMap', materialDef.occlusionTexture ) );

                        if ( materialDef.occlusionTexture.strength !== undefined ) {

                                materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;

                        }

                }

                if ( materialDef.emissiveFactor !== undefined && materialType !== MeshBasicMaterial ) {

                        materialParams.emissive = new Color().fromArray( materialDef.emissiveFactor );

                }

                if ( materialDef.emissiveTexture !== undefined && materialType !== MeshBasicMaterial ) {

                        pending.push( parser.assignTexture( materialParams, 'emissiveMap', materialDef.emissiveTexture ) );

                }

                return Promise.all( pending ).then( function () {

                        var material;

                        if ( materialType === GLTFMeshStandardSGMaterial ) {

                                material = extensions[ EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS ].createMaterial( materialParams );

                        } else {

                                material = new materialType( materialParams );

                        }

                        if ( materialDef.name ) material.name = materialDef.name;

                        // baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
                        if ( material.map ) material.map.encoding = sRGBEncoding;
                        if ( material.emissiveMap ) material.emissiveMap.encoding = sRGBEncoding;

                        assignExtrasToUserData( material, materialDef );

                        parser.associations.set( material, { type: 'materials', index: materialIndex } );

                        if ( materialDef.extensions ) addUnknownExtensionsToUserData( extensions, material, materialDef );

                        return material;

                } );

        };

        /** When Object3D instances are targeted by animation, they need unique names. */
        GLTFParser.prototype.createUniqueName = function ( originalName ) {

                var name = PropertyBinding.sanitizeNodeName( originalName || '' );

                for ( var i = 1; this.nodeNamesUsed[ name ]; ++ i ) {

                        name = originalName + '_' + i;

                }

                this.nodeNamesUsed[ name ] = true;

                return name;

        };

        /**
         * @param {BufferGeometry} geometry
         * @param {GLTF.Primitive} primitiveDef
         * @param {GLTFParser} parser
         */
        function computeBounds( geometry, primitiveDef, parser ) {

                var attributes = primitiveDef.attributes;

                var box = new Box3();

                if ( attributes.POSITION !== undefined ) {

                        var accessor = parser.json.accessors[ attributes.POSITION ];

                        var min = accessor.min;
                        var max = accessor.max;

                        // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

                        if ( min !== undefined && max !== undefined ) {

                                box.set(
                                        new Vector3( min[ 0 ], min[ 1 ], min[ 2 ] ),
                                        new Vector3( max[ 0 ], max[ 1 ], max[ 2 ] ) );

                        } else {

                                console.warn( 'THREE.GLTFLoader: Missing min/max properties for accessor POSITION.' );

                                return;

                        }

                } else {

                        return;

                }

                var targets = primitiveDef.targets;

                if ( targets !== undefined ) {

                        var maxDisplacement = new Vector3();
                        var vector = new Vector3();

                        for ( var i = 0, il = targets.length; i < il; i ++ ) {

                                var target = targets[ i ];

                                if ( target.POSITION !== undefined ) {

                                        var accessor = parser.json.accessors[ target.POSITION ];
                                        var min = accessor.min;
                                        var max = accessor.max;

                                        // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

                                        if ( min !== undefined && max !== undefined ) {

                                                // we need to get max of absolute components because target weight is [-1,1]
                                                vector.setX( Math.max( Math.abs( min[ 0 ] ), Math.abs( max[ 0 ] ) ) );
                                                vector.setY( Math.max( Math.abs( min[ 1 ] ), Math.abs( max[ 1 ] ) ) );
                                                vector.setZ( Math.max( Math.abs( min[ 2 ] ), Math.abs( max[ 2 ] ) ) );

                                                // Note: this assumes that the sum of all weights is at most 1. This isn't quite correct - it's more conservative
                                                // to assume that each target can have a max weight of 1. However, for some use cases - notably, when morph targets
                                                // are used to implement key-frame animations and as such only two are active at a time - this results in very large
                                                // boxes. So for now we make a box that's sometimes a touch too small but is hopefully mostly of reasonable size.
                                                maxDisplacement.max( vector );

                                        } else {

                                                console.warn( 'THREE.GLTFLoader: Missing min/max properties for accessor POSITION.' );

                                        }

                                }

                        }

                        // As per comment above this box isn't conservative, but has a reasonable size for a very large number of morph targets.
                        box.expandByVector( maxDisplacement );

                }

                geometry.boundingBox = box;

                var sphere = new Sphere();

                box.getCenter( sphere.center );
                sphere.radius = box.min.distanceTo( box.max ) / 2;

                geometry.boundingSphere = sphere;

        }

        /**
         * @param {BufferGeometry} geometry
         * @param {GLTF.Primitive} primitiveDef
         * @param {GLTFParser} parser
         * @return {Promise<BufferGeometry>}
         */
        function addPrimitiveAttributes( geometry, primitiveDef, parser ) {

                var attributes = primitiveDef.attributes;

                var pending = [];

                function assignAttributeAccessor( accessorIndex, attributeName ) {

                        return parser.getDependency( 'accessor', accessorIndex )
                                .then( function ( accessor ) {

                                        geometry.setAttribute( attributeName, accessor );

                                } );

                }

                for ( var gltfAttributeName in attributes ) {

                        var threeAttributeName = ATTRIBUTES[ gltfAttributeName ] || gltfAttributeName.toLowerCase();

                        // Skip attributes already provided by e.g. Draco extension.
                        if ( threeAttributeName in geometry.attributes ) continue;

                        pending.push( assignAttributeAccessor( attributes[ gltfAttributeName ], threeAttributeName ) );

                }

                if ( primitiveDef.indices !== undefined && ! geometry.index ) {

                        var accessor = parser.getDependency( 'accessor', primitiveDef.indices ).then( function ( accessor ) {

                                geometry.setIndex( accessor );

                        } );

                        pending.push( accessor );

                }

                assignExtrasToUserData( geometry, primitiveDef );

                computeBounds( geometry, primitiveDef, parser );

                return Promise.all( pending ).then( function () {

                        return primitiveDef.targets !== undefined
                                ? addMorphTargets( geometry, primitiveDef.targets, parser )
                                : geometry;

                } );

        }

        /**
         * @param {BufferGeometry} geometry
         * @param {Number} drawMode
         * @return {BufferGeometry}
         */
        function toTrianglesDrawMode( geometry, drawMode ) {

                var index = geometry.getIndex();

                // generate index if not present

                if ( index === null ) {

                        var indices = [];

                        var position = geometry.getAttribute( 'position' );

                        if ( position !== undefined ) {

                                for ( var i = 0; i < position.count; i ++ ) {

                                        indices.push( i );

                                }

                                geometry.setIndex( indices );
                                index = geometry.getIndex();

                        } else {

                                console.error( 'THREE.GLTFLoader.toTrianglesDrawMode(): Undefined position attribute. Processing not possible.' );
                                return geometry;

                        }

                }

                //

                var numberOfTriangles = index.count - 2;
                var newIndices = [];

                if ( drawMode === TriangleFanDrawMode ) {

                        // gl.TRIANGLE_FAN

                        for ( var i = 1; i <= numberOfTriangles; i ++ ) {

                                newIndices.push( index.getX( 0 ) );
                                newIndices.push( index.getX( i ) );
                                newIndices.push( index.getX( i + 1 ) );

                        }

                } else {

                        // gl.TRIANGLE_STRIP

                        for ( var i = 0; i < numberOfTriangles; i ++ ) {

                                if ( i % 2 === 0 ) {

                                        newIndices.push( index.getX( i ) );
                                        newIndices.push( index.getX( i + 1 ) );
                                        newIndices.push( index.getX( i + 2 ) );


                                } else {

                                        newIndices.push( index.getX( i + 2 ) );
                                        newIndices.push( index.getX( i + 1 ) );
                                        newIndices.push( index.getX( i ) );

                                }

                        }

                }

                if ( ( newIndices.length / 3 ) !== numberOfTriangles ) {

                        console.error( 'THREE.GLTFLoader.toTrianglesDrawMode(): Unable to generate correct amount of triangles.' );

                }

                // build final geometry

                var newGeometry = geometry.clone();
                newGeometry.setIndex( newIndices );

                return newGeometry;

        }

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
         *
         * Creates BufferGeometries from primitives.
         *
         * @param {Array<GLTF.Primitive>} primitives
         * @return {Promise<Array<BufferGeometry>>}
         */
        GLTFParser.prototype.loadGeometries = function ( primitives ) {

                var parser = this;
                var extensions = this.extensions;
                var cache = this.primitiveCache;

                function createDracoPrimitive( primitive ) {

                        return extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ]
                                .decodePrimitive( primitive, parser )
                                .then( function ( geometry ) {

                                        return addPrimitiveAttributes( geometry, primitive, parser );

                                } );

                }

                var pending = [];

                for ( var i = 0, il = primitives.length; i < il; i ++ ) {

                        var primitive = primitives[ i ];
                        var cacheKey = createPrimitiveKey( primitive );

                        // See if we've already created this geometry
                        var cached = cache[ cacheKey ];

                        if ( cached ) {

                                // Use the cached geometry if it exists
                                pending.push( cached.promise );

                        } else {

                                var geometryPromise;

                                if ( primitive.extensions && primitive.extensions[ EXTENSIONS.KHR_DRACO_MESH_COMPRESSION ] ) {

                                        // Use DRACO geometry if available
                                        geometryPromise = createDracoPrimitive( primitive );

                                } else {

                                        // Otherwise create a new geometry
                                        geometryPromise = addPrimitiveAttributes( new BufferGeometry(), primitive, parser );

                                }

                                // Cache this geometry
                                cache[ cacheKey ] = { primitive: primitive, promise: geometryPromise };

                                pending.push( geometryPromise );

                        }

                }

                return Promise.all( pending );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
         * @param {number} meshIndex
         * @return {Promise<Group|Mesh|SkinnedMesh>}
         */
        GLTFParser.prototype.loadMesh = function ( meshIndex ) {

                var parser = this;
                var json = this.json;

                var meshDef = json.meshes[ meshIndex ];
                var primitives = meshDef.primitives;

                var pending = [];

                for ( var i = 0, il = primitives.length; i < il; i ++ ) {

                        var material = primitives[ i ].material === undefined
                                ? createDefaultMaterial( this.cache )
                                : this.getDependency( 'material', primitives[ i ].material );

                        pending.push( material );

                }

                pending.push( parser.loadGeometries( primitives ) );

                return Promise.all( pending ).then( function ( results ) {

                        var materials = results.slice( 0, results.length - 1 );
                        var geometries = results[ results.length - 1 ];

                        var meshes = [];

                        for ( var i = 0, il = geometries.length; i < il; i ++ ) {

                                var geometry = geometries[ i ];
                                var primitive = primitives[ i ];

                                // 1. create Mesh

                                var mesh;

                                var material = materials[ i ];

                                if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
                                        primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
                                        primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
                                        primitive.mode === undefined ) {

                                        // .isSkinnedMesh isn't in glTF spec. See ._markDefs()
                                        mesh = meshDef.isSkinnedMesh === true
                                                ? new SkinnedMesh( geometry, material )
                                                : new Mesh( geometry, material );

                                        if ( mesh.isSkinnedMesh === true && ! mesh.geometry.attributes.skinWeight.normalized ) {

                                                // we normalize floating point skin weight array to fix malformed assets (see #15319)
                                                // it's important to skip this for non-float32 data since normalizeSkinWeights assumes non-normalized inputs
                                                mesh.normalizeSkinWeights();

                                        }

                                        if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ) {

                                                mesh.geometry = toTrianglesDrawMode( mesh.geometry, TriangleStripDrawMode );

                                        } else if ( primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ) {

                                                mesh.geometry = toTrianglesDrawMode( mesh.geometry, TriangleFanDrawMode );

                                        }

                                } else if ( primitive.mode === WEBGL_CONSTANTS.LINES ) {

                                        mesh = new LineSegments( geometry, material );

                                } else if ( primitive.mode === WEBGL_CONSTANTS.LINE_STRIP ) {

                                        mesh = new Line( geometry, material );

                                } else if ( primitive.mode === WEBGL_CONSTANTS.LINE_LOOP ) {

                                        mesh = new LineLoop( geometry, material );

                                } else if ( primitive.mode === WEBGL_CONSTANTS.POINTS ) {

                                        mesh = new Points( geometry, material );

                                } else {

                                        throw new Error( 'THREE.GLTFLoader: Primitive mode unsupported: ' + primitive.mode );

                                }

                                if ( Object.keys( mesh.geometry.morphAttributes ).length > 0 ) {

                                        updateMorphTargets( mesh, meshDef );

                                }

                                mesh.name = parser.createUniqueName( meshDef.name || ( 'mesh_' + meshIndex ) );

                                assignExtrasToUserData( mesh, meshDef );

                                parser.assignFinalMaterial( mesh );

                                meshes.push( mesh );

                        }

                        if ( meshes.length === 1 ) {

                                return meshes[ 0 ];

                        }

                        var group = new Group();

                        for ( var i = 0, il = meshes.length; i < il; i ++ ) {

                                group.add( meshes[ i ] );

                        }

                        return group;

                } );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
         * @param {number} cameraIndex
         * @return {Promise<THREE.Camera>}
         */
        GLTFParser.prototype.loadCamera = function ( cameraIndex ) {

                var camera;
                var cameraDef = this.json.cameras[ cameraIndex ];
                var params = cameraDef[ cameraDef.type ];

                if ( ! params ) {

                        console.warn( 'THREE.GLTFLoader: Missing camera parameters.' );
                        return;

                }

                if ( cameraDef.type === 'perspective' ) {

                        camera = new PerspectiveCamera( MathUtils.radToDeg( params.yfov ), params.aspectRatio || 1, params.znear || 1, params.zfar || 2e6 );

                } else if ( cameraDef.type === 'orthographic' ) {

                        camera = new OrthographicCamera( - params.xmag, params.xmag, params.ymag, - params.ymag, params.znear, params.zfar );

                }

                if ( cameraDef.name ) camera.name = this.createUniqueName( cameraDef.name );

                assignExtrasToUserData( camera, cameraDef );

                return Promise.resolve( camera );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
         * @param {number} skinIndex
         * @return {Promise<Object>}
         */
        GLTFParser.prototype.loadSkin = function ( skinIndex ) {

                var skinDef = this.json.skins[ skinIndex ];

                var skinEntry = { joints: skinDef.joints };

                if ( skinDef.inverseBindMatrices === undefined ) {

                        return Promise.resolve( skinEntry );

                }

                return this.getDependency( 'accessor', skinDef.inverseBindMatrices ).then( function ( accessor ) {

                        skinEntry.inverseBindMatrices = accessor;

                        return skinEntry;

                } );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
         * @param {number} animationIndex
         * @return {Promise<AnimationClip>}
         */
        GLTFParser.prototype.loadAnimation = function ( animationIndex ) {

                var json = this.json;

                var animationDef = json.animations[ animationIndex ];

                var pendingNodes = [];
                var pendingInputAccessors = [];
                var pendingOutputAccessors = [];
                var pendingSamplers = [];
                var pendingTargets = [];

                for ( var i = 0, il = animationDef.channels.length; i < il; i ++ ) {

                        var channel = animationDef.channels[ i ];
                        var sampler = animationDef.samplers[ channel.sampler ];
                        var target = channel.target;
                        var name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
                        var input = animationDef.parameters !== undefined ? animationDef.parameters[ sampler.input ] : sampler.input;
                        var output = animationDef.parameters !== undefined ? animationDef.parameters[ sampler.output ] : sampler.output;

                        pendingNodes.push( this.getDependency( 'node', name ) );
                        pendingInputAccessors.push( this.getDependency( 'accessor', input ) );
                        pendingOutputAccessors.push( this.getDependency( 'accessor', output ) );
                        pendingSamplers.push( sampler );
                        pendingTargets.push( target );

                }

                return Promise.all( [

                        Promise.all( pendingNodes ),
                        Promise.all( pendingInputAccessors ),
                        Promise.all( pendingOutputAccessors ),
                        Promise.all( pendingSamplers ),
                        Promise.all( pendingTargets )

                ] ).then( function ( dependencies ) {

                        var nodes = dependencies[ 0 ];
                        var inputAccessors = dependencies[ 1 ];
                        var outputAccessors = dependencies[ 2 ];
                        var samplers = dependencies[ 3 ];
                        var targets = dependencies[ 4 ];

                        var tracks = [];

                        for ( var i = 0, il = nodes.length; i < il; i ++ ) {

                                var node = nodes[ i ];
                                var inputAccessor = inputAccessors[ i ];
                                var outputAccessor = outputAccessors[ i ];
                                var sampler = samplers[ i ];
                                var target = targets[ i ];

                                if ( node === undefined ) continue;

                                node.updateMatrix();
                                node.matrixAutoUpdate = true;

                                var TypedKeyframeTrack;

                                switch ( PATH_PROPERTIES[ target.path ] ) {

                                        case PATH_PROPERTIES.weights:

                                                TypedKeyframeTrack = NumberKeyframeTrack;
                                                break;

                                        case PATH_PROPERTIES.rotation:

                                                TypedKeyframeTrack = QuaternionKeyframeTrack;
                                                break;

                                        case PATH_PROPERTIES.position:
                                        case PATH_PROPERTIES.scale:
                                        default:

                                                TypedKeyframeTrack = VectorKeyframeTrack;
                                                break;

                                }

                                var targetName = node.name ? node.name : node.uuid;

                                var interpolation = sampler.interpolation !== undefined ? INTERPOLATION[ sampler.interpolation ] : InterpolateLinear;

                                var targetNames = [];

                                if ( PATH_PROPERTIES[ target.path ] === PATH_PROPERTIES.weights ) {

                                        // Node may be a Group (glTF mesh with several primitives) or a Mesh.
                                        node.traverse( function ( object ) {

                                                if ( object.isMesh === true && object.morphTargetInfluences ) {

                                                        targetNames.push( object.name ? object.name : object.uuid );

                                                }

                                        } );

                                } else {

                                        targetNames.push( targetName );

                                }

                                var outputArray = outputAccessor.array;

                                if ( outputAccessor.normalized ) {

                                        var scale;

                                        if ( outputArray.constructor === Int8Array ) {

                                                scale = 1 / 127;

                                        } else if ( outputArray.constructor === Uint8Array ) {

                                                scale = 1 / 255;

                                        } else if ( outputArray.constructor == Int16Array ) {

                                                scale = 1 / 32767;

                                        } else if ( outputArray.constructor === Uint16Array ) {

                                                scale = 1 / 65535;

                                        } else {

                                                throw new Error( 'THREE.GLTFLoader: Unsupported output accessor component type.' );

                                        }

                                        var scaled = new Float32Array( outputArray.length );

                                        for ( var j = 0, jl = outputArray.length; j < jl; j ++ ) {

                                                scaled[ j ] = outputArray[ j ] * scale;

                                        }

                                        outputArray = scaled;

                                }

                                for ( var j = 0, jl = targetNames.length; j < jl; j ++ ) {

                                        var track = new TypedKeyframeTrack(
                                                targetNames[ j ] + '.' + PATH_PROPERTIES[ target.path ],
                                                inputAccessor.array,
                                                outputArray,
                                                interpolation
                                        );

                                        // Override interpolation with custom factory method.
                                        if ( sampler.interpolation === 'CUBICSPLINE' ) {

                                                track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline( result ) {

                                                        // A CUBICSPLINE keyframe in glTF has three output values for each input value,
                                                        // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
                                                        // must be divided by three to get the interpolant's sampleSize argument.

                                                        return new GLTFCubicSplineInterpolant( this.times, this.values, this.getValueSize() / 3, result );

                                                };

                                                // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
                                                track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;

                                        }

                                        tracks.push( track );

                                }

                        }

                        var name = animationDef.name ? animationDef.name : 'animation_' + animationIndex;

                        return new AnimationClip( name, undefined, tracks );

                } );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
         * @param {number} nodeIndex
         * @return {Promise<Object3D>}
         */
        GLTFParser.prototype.loadNode = function ( nodeIndex ) {

                var json = this.json;
                var extensions = this.extensions;
                var parser = this;

                var nodeDef = json.nodes[ nodeIndex ];

                // reserve node's name before its dependencies, so the root has the intended name.
                var nodeName = nodeDef.name ? parser.createUniqueName( nodeDef.name ) : '';

                return ( function () {

                        var pending = [];

                        if ( nodeDef.mesh !== undefined ) {

                                pending.push( parser.getDependency( 'mesh', nodeDef.mesh ).then( function ( mesh ) {

                                        var node = parser._getNodeRef( parser.meshCache, nodeDef.mesh, mesh );

                                        // if weights are provided on the node, override weights on the mesh.
                                        if ( nodeDef.weights !== undefined ) {

                                                node.traverse( function ( o ) {

                                                        if ( ! o.isMesh ) return;

                                                        for ( var i = 0, il = nodeDef.weights.length; i < il; i ++ ) {

                                                                o.morphTargetInfluences[ i ] = nodeDef.weights[ i ];

                                                        }

                                                } );

                                        }

                                        return node;

                                } ) );

                        }

                        if ( nodeDef.camera !== undefined ) {

                                pending.push( parser.getDependency( 'camera', nodeDef.camera ).then( function ( camera ) {

                                        return parser._getNodeRef( parser.cameraCache, nodeDef.camera, camera );

                                } ) );

                        }

                        parser._invokeAll( function ( ext ) {

                                return ext.createNodeAttachment && ext.createNodeAttachment( nodeIndex );

                        } ).forEach( function ( promise ) {

                                pending.push( promise );

                        } );

                        return Promise.all( pending );

                }() ).then( function ( objects ) {

                        var node;

                        // .isBone isn't in glTF spec. See ._markDefs
                        if ( nodeDef.isBone === true ) {

                                node = new Bone();

                        } else if ( objects.length > 1 ) {

                                node = new Group();

                        } else if ( objects.length === 1 ) {

                                node = objects[ 0 ];

                        } else {

                                node = new Object3D();

                        }

                        if ( node !== objects[ 0 ] ) {

                                for ( var i = 0, il = objects.length; i < il; i ++ ) {

                                        node.add( objects[ i ] );

                                }

                        }

                        if ( nodeDef.name ) {

                                node.userData.name = nodeDef.name;
                                node.name = nodeName;

                        }

                        assignExtrasToUserData( node, nodeDef );

                        if ( nodeDef.extensions ) addUnknownExtensionsToUserData( extensions, node, nodeDef );

                        if ( nodeDef.matrix !== undefined ) {

                                var matrix = new Matrix4();
                                matrix.fromArray( nodeDef.matrix );
                                node.applyMatrix4( matrix );

                        } else {

                                if ( nodeDef.translation !== undefined ) {

                                        node.position.fromArray( nodeDef.translation );

                                }

                                if ( nodeDef.rotation !== undefined ) {

                                        node.quaternion.fromArray( nodeDef.rotation );

                                }

                                if ( nodeDef.scale !== undefined ) {

                                        node.scale.fromArray( nodeDef.scale );

                                }

                        }

                        parser.associations.set( node, { type: 'nodes', index: nodeIndex } );

                        return node;

                } );

        };

        /**
         * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
         * @param {number} sceneIndex
         * @return {Promise<Group>}
         */
        GLTFParser.prototype.loadScene = function () {

                // scene node hierachy builder

                function buildNodeHierachy( nodeId, parentObject, json, parser ) {

                        var nodeDef = json.nodes[ nodeId ];

                        return parser.getDependency( 'node', nodeId ).then( function ( node ) {

                                if ( nodeDef.skin === undefined ) return node;

                                // build skeleton here as well

                                var skinEntry;

                                return parser.getDependency( 'skin', nodeDef.skin ).then( function ( skin ) {

                                        skinEntry = skin;

                                        var pendingJoints = [];

                                        for ( var i = 0, il = skinEntry.joints.length; i < il; i ++ ) {

                                                pendingJoints.push( parser.getDependency( 'node', skinEntry.joints[ i ] ) );

                                        }

                                        return Promise.all( pendingJoints );

                                } ).then( function ( jointNodes ) {

                                        node.traverse( function ( mesh ) {

                                                if ( ! mesh.isMesh ) return;

                                                var bones = [];
                                                var boneInverses = [];

                                                for ( var j = 0, jl = jointNodes.length; j < jl; j ++ ) {

                                                        var jointNode = jointNodes[ j ];

                                                        if ( jointNode ) {

                                                                bones.push( jointNode );

                                                                var mat = new Matrix4();

                                                                if ( skinEntry.inverseBindMatrices !== undefined ) {

                                                                        mat.fromArray( skinEntry.inverseBindMatrices.array, j * 16 );

                                                                }

                                                                boneInverses.push( mat );

                                                        } else {

                                                                console.warn( 'THREE.GLTFLoader: Joint "%s" could not be found.', skinEntry.joints[ j ] );

                                                        }

                                                }

                                                mesh.bind( new Skeleton( bones, boneInverses ), mesh.matrixWorld );

                                        } );

                                        return node;

                                } );

                        } ).then( function ( node ) {

                                // build node hierachy

                                parentObject.add( node );

                                var pending = [];

                                if ( nodeDef.children ) {

                                        var children = nodeDef.children;

                                        for ( var i = 0, il = children.length; i < il; i ++ ) {

                                                var child = children[ i ];
                                                pending.push( buildNodeHierachy( child, node, json, parser ) );

                                        }

                                }

                                return Promise.all( pending );

                        } );

                }

                return function loadScene( sceneIndex ) {

                        var json = this.json;
                        var extensions = this.extensions;
                        var sceneDef = this.json.scenes[ sceneIndex ];
                        var parser = this;

                        // Loader returns Group, not Scene.
                        // See: https://github.com/mrdoob/three.js/issues/18342#issuecomment-578981172
                        var scene = new Group();
                        if ( sceneDef.name ) scene.name = parser.createUniqueName( sceneDef.name );

                        assignExtrasToUserData( scene, sceneDef );

                        if ( sceneDef.extensions ) addUnknownExtensionsToUserData( extensions, scene, sceneDef );

                        var nodeIds = sceneDef.nodes || [];

                        var pending = [];

                        for ( var i = 0, il = nodeIds.length; i < il; i ++ ) {

                                pending.push( buildNodeHierachy( nodeIds[ i ], scene, json, parser ) );

                        }

                        return Promise.all( pending ).then( function () {

                                return scene;

                        } );

                };

        }();

        return GLTFLoader;

} )();

export { GLTFLoader };
